thus \(\bar{R}_{2}\in Z^{2}(E) \subset \mathcal {Z}^{2}(E) \) , i.e., it is a closed 2-form and \(d^{2}\theta _{0}\in \Lambda ^{2}(E) \)  is a global 2-form. We follow now a classical way for constructing characteristic classes (for example [1]}),
